Reagents for prothrombin time measurement are produced, for example, by mixing a tissue factor, a phospholipid, and a buffer solution containing a surfactant, and removing the surfactant from the resulting mixture (see, for example, U.S. 2004/086953 A). These reagents are usually stored in a freeze-dried state, for storage, transport, and others. Freeze-dried reagents for prothrombin time measurement are utilized in a state of being re-dissolved in an appropriate solvent when used.
However, reagents for prothrombin time measurement containing a tissue factor may cause variations in measurements of prothrombin time before and after freeze drying of the reagent.
The present invention provides a reagent for prothrombin time measurement that can control variations in measurements of prothrombin time before and after freeze drying of the reagent, a method for production thereof, and a method for measurement of prothrombin time.